To achieve proper phase commutation in an electronically commutated motor drive, such as, for example, a switched reluctance motor drive, a shaft position sensor is generally needed for feeding back a rotor position signal to a controller. Disadvantageously, such shaft position sensors, e.g. resolvers, are generally delicate and costly. Specifically, one shortcoming of such devices is that an electrical pulse which is generated for each passing tooth of the rotor is typically broad and decreases in magnitude as rotor speed decreases. On the other hand, conventional shaft position sensors utilizing the Wiegand effect produce strong, sharp signals, even at low speeds and zero speed, upon the reversal of an imposed magnetic field. Specifically, the Wiegand effect involves the generation of sharp electrical pulses in a coil wrapped around, or otherwise situated in close proximity to, a Wiegand wire in the presence of a changing magnetic field. A Wiegand wire has a relatively hard outer shell of high-permeability magnetic material and a relatively soft core of low-permeability magnetic material, or vice versa. The field reversal in a Wiegand-effect device is typically accomplished by attaching permanent magnet material to the rotating shaft and magnetizing it with alternating north and south poles. When the applied magnetic field reverses direction, the direction of magnetization in the soft core abruptly changes its direction of magnetization to match that of the applied field, generating a sharp voltage pulse across the coil. Thereafter, when the applied magnetic field again reverses direction, the direction of magnetization in the core again reverses direction and generates another sharp voltage pulse, but of opposite polarity. Unfortunately, such conventional Wiegand-effect shaft position sensors employing permanent magnets mounted on the rotor are unsuitable for use in high-speed machines having highly stressed rotors.